1. Field of the Invention
This invention relates to the treatment of metal surfaces for corrosion protection. More particularly, this invention relates to the pretreatment of metal, particularly ferrous metal surfaces to passivate the surface and improve subsequent coating properties.
2. Brief Description of the Prior Art
It is well known in the prior art that chromic acid pretreatments passivate and improve the corrosion resistance and coating properties of metals, particularly ferrous metal surfaces. However, chromic acid pretreatments are undesirable because chromic acid is toxic and its effluent creates serious pollution problems. The present invention resides in the discovery that ascorbic acid-containing compositions, free of beta-diketones, and preferably in combination with molybdenum, can be used to passivate metal surfaces, particularly ferrous metal surfaces. Besides improving the corrosion resistance and subsequent coating properties of the treated metal surfaces, the compositions employed in the present invention are ecologically acceptable.